1. Field of the Invention
The present invention relates to toner used for copiers, laser beam printers (LBP), plain paper facsimiles, color electrophotography (PPC), color LBPs or color facsimiles and a method for producing the same.
2. Description of the Prior Art
Recently, electrophotographic apparatuses, which commonly were used in offices, have been used increasingly for personal purposes, so that technologies to achieve compact or maintenance-free electrophotographic apparatuses are required. To meet this end, it is necessary to improve maintenance properties such as recycling of waste toner and reducing the emission of ozone.
It is well-know that toner for electrostatic charge development used in an electrophotographic method generally includes a resin component, a coloring component including a pigment or a dye, a plasticizer, a charge controlling agent, and an additive, if necessary, such as a releasing agent. As the resin component, natural or synthetic resin is used alone or in combination. An additive is pre-mixed in an appropriate ratio and the resulting mixture is heated and kneaded by thermal melting, and pulverized by an air stream collision board system, and fine powder is classified to complete a toner base. Thereafter, an external additive is added to the toner base externally so as to complete the toner. The single component development typically uses toner only, and in the two component development system, the developer material includes toner and carrier comprising magnetic granules.
For color copiers, a photoconductive member is charged by corona discharge with a charger, and then is exposed to optical signals for latent images for each color to form electrostatic latent images. The latent images are developed by a first color toner, e.g., yellow toner, to form visible images. Thereafter, a transfer material charged with a polarity reverse to that of the charged yellow toner is contacted with the photoconductive member so that the yellow toner images formed on the photoconductive member are transferred thereto. The photoconductive member is cleaned by removing residual toner that has not been transferred, and the development and transfer of the first color toner ends with discharging the photoconductive member. Thereafter, the same operations as those for the yellow toner are repeated for toners for other colors such as magenta and cyan. The toner images of the colors are superimposed on the transfer material so as to form color images. Then, the superimposed toner images are transferred to a transfer paper charged with a polarity reverse to that of the toner, and fixed. Thus, the copying operation ends.
As a method for forming color images, a transfer drum method and a successive superimposition method generally are used. In the transfer drum method, toner images for each color are formed on a single photoconductive member one after another, and a transfer material wound on a transfer drum is opposed to the photoconductive member repeatedly by rotating the drum so that the toner images for each color formed sequentially are superimposed and transferred to the transfer material. In the successive superimposition method, a plurality of image formation sections are provided, and toner images for each color are transferred to a transfer material conveyed by a belt sequentially while moving the image formation sections so that the color images are superimposed. One example using the transfer drum method is a color image formation apparatus disclosed in Japanese Laid-Open Patent Publication (Tokkai-Hei) No. 1-252982. One example of a color image formation apparatus using the successive transfer method is disclosed in Japanese Laid-Open Patent Publication (Tokkai-Hei) No. 1-250970. In this conventional example, four image formation stations, each of which includes a photoconductive member, optical scanning means or the like, are arranged to form images for four colors. A paper conveyed by a belt passes below each photoconductive member so that color toner images are superimposed. As another method for forming color images by superimposing toner images for different colors on a transfer material, Japanese Laid-Open Patent Publication (Tokkai-Hei) No. 2-212867 discloses the following method. Toner images for each color formed on a photoconductive member sequentially are superimposed on an intermediate transfer material, and then the toner images on the intermediate transfer material are transferred to a transfer paper collectively.
Further, Japanese Laid-Open Patent Publication (Tokkai-Sho) No. 59-148067 discloses toner using as a resin an unsaturated ethylene based polymer including a low molecular weight and a high molecular weight portion, where the peak value of the low molecular weight and Mw/Mn are defined, and containing polyolefin having a specific softening point. This disclosure is intended to provide fixability and an anti-offset property. Japanese Laid-Open Patent Publication (Tokkai-Sho) No. 56-158340 discloses toner comprising a resin including a specific low molecular weight polymer component and a specific high molecular weight polymer component as the main component. The low molecular weight component is used to provide fixability, and the high molecular weight component is used to provide the anti-offset property. Further, Japanese Laid-Open Patent Publication (Tokkai-Sho) No. 58-223155 discloses toner having containing a resin including an unsaturated ethylene based polymer having the local maximum in molecular weight ranges of 1000 to 10000 and 200000 to 1000000 and Mw/Mn of 10 to 40, and a polyolefin having a specific softening point. The low molecular weight component is used to provide fixability, and the high molecular weight component and the polyolefin are used to provide the anti-offset property.
However, when the melt viscosity of a binding resin is reduced or a low molecular weight resin is used in order to raise the fixing strength with high-speed machines, the so-called xe2x80x9cspentxe2x80x9d, which is caused by toner adhering to carriers, may occur during long term use in the case of two component development. In the case of the single component development, the toner is likely to adhere to a doctor blade or a development sleeve, so that the stress resistance property of the toner deteriorates. When the toner is used in a low-speed machine, offset caused by toner adhering to a heat roller may occur at the time of fixing. Further, blocking caused by toner particles fused with each other may occur during long period storage.
On the other hand, the successive transfer system includes image formation positions corresponding in number to the number of colors, and a paper is allowed to pass by the image formation positions one after another. Therefore, a transfer drum is not required. However, this system requires a plurality of latent image formation means, such as laser optical systems, for forming latent images on the photoconductive member corresponding in number to the number of colors. This complicates the structure and makes the apparatus expensive. Moreover, since there are a plurality of image formation positions, positions of portions where images for different colors are formed may not match each other, the rotation axis may be off center, or the parallelism of the portions may not match. These factors prevent the colors from being placed in intended positions and make it difficult to obtain high quality images stably. In particular, it is necessary to register the latent images for different colors precisely by the latent image formation means. As shown in Japanese Laid-Open Patent Publication (Tokkai-Hei) No. 1-250970, considerable efforts and a complicated configuration for an image exposure system, which is a latent formation means, are required.
Furthermore, in the example of Japanese Laid-Open Patent Publication (Tokkai-Hei) No. 2-212867 employing an intermediate transfer material, toner images for all colors are formed on one and the same photoconductive member. Therefore, a plurality of developing devices are required to be provided around the single photoconductive member, and therefore the photoconductive member should be large. Furthermore, the photoconductive member is belt-shaped, which is difficult to handle. Moreover, at the time of replacement of each development device for maintenance, matching adjustment is required, or at the time of replacement of the photoconductive member, position adjustment relative to each development device is required. Thus, the maintenance of the development device for each color and the photoconductive member is difficult.
Furthermore, a process for producing toner includes a pre-blending treatment, a kneading treatment, a pulverization treatment, a classification treatment and an external addition treatment. The classification treatment is intended to classify toner powder so as to obtain a predetermined particle size distribution. In the current system, the toner powder that has been classified out is disposed of, because if the removed toner powder is used to be blended again, fog increases. Especially polypropylene or polyethylene wax, which is added to improve a releasing property, increases fog significantly. The reuse of the toner powder, which is generated in an amount of about 10 to 20 wt %, would result in more effective use of resources.
Therefore, with the foregoing in mind, it is a first object of the present invention to provide toner having improved dispersibility of an internal additive such as wax in a binding resin and uniform charge distribution, and a method for producing the same.
It is a second object of the present invention to provide toner for full color electrophotography that allows oilless fixation, that is, fixation without applying oil, and a method for producing the same.
It is a third object of the present invention to provide toner that improves the dispersibility of an additive without degrading resin characteristics even if a high functional binding resin is used, and maintains a stable development property, and to provide a method for producing the same.
It is a fourth object of the present invention to provide toner that can achieve both fixability and anti-offset properties when used in machines having widely different process speeds, and has excellent dispersibility and stable chargeability so that high quality images are reproduced, and to provide a method for producing the same.
It is a fifth object of the present invention to provide toner that prevents thinning-out or scattering during transfer in an electrophotographic method employing a conductive elastic roller or an intermediate transfer member and achieves a high transfer efficiency, and to provide a method for producing the same.
It is a sixth object of the present invention to provide toner that prevents filming on a photoconductive member and an intermediate transfer member, and a method for producing the same.
It is a seventh object of the present invention to provide toner that allows development with waste toner without reducing the charge amount and the flowability of a developer and without generating agglomerates, achieves a long life, and allows reduction of global environmental pollution and reuse of the resources, and to provide a method for producing the same.
It is an eighth object of the present invention to provide toner that provides stable images even if classified-out toner powder is reused in blending, and a method for producing the same.
A first toner of the present invention comprises a binding resin, a colorant, and an ester based wax having an iodine value of not more than 25 and a saponification value of 30 to 300.
It is preferable that the toner comprises 1 to 10 parts by weight of the colorant and 0.1 to 10 parts by weight of the ester based wax per 100 parts by weight of the binding resin.
It is preferable that the toner comprises 3 to 8 parts by weight of the colorant and 0.5 to 8 parts by weight of the ester based wax per 100 parts by weight of the binding resin.
It is preferable that the toner further comprises a polyolefin wax that is graft modified with unsaturated carboxylic acid and has an oxygen number of 6 to 200 mgKOH/g.
It is preferable that the toner comprises 0.1 to 10 parts by weight of the polyolefin wax per 100 parts by weight of the binding resin.
It is preferable that a melting point of the ester based wax according to the DSC method is 50 to 100xc2x0 C.
It is preferable that a volume increase ratio of the ester based wax at a temperature equal to or more than the melting point is 2 to 30%.
It is preferable that a heating loss of the ester based wax at a temperature of 220xc2x0 C. is not more than 8 wt %.
It is preferable that the binding resin is formed by adding the ester based wax to a solution, and removing a solvent.
It is preferable that the ester based wax is at least one substance selected from the group consisting of meadowfoam oil derivatives and jojoba oil derivatives.
It is preferable that the jojoba oil derivative is at least one selected from the group consisting of jojoba oil fatty acid, a metal salt of jojoba oil fatty acid, jojoba oil fatty acid ester, hydrogenated jojoba oil, jojoba oil amide, homojojoba oil amide, jojoba oil triester, maleic acid derivatives from epoxidized jojoba oil, and isocyanate polymer of jojoba oil fatty acid polyhydric alcohol ester.
It is preferable that the jojoba oil triester is obtained by epoxidizing jojoba oil, hydrating the resultant for ring-opening, and then effecting acylation.
It is preferable that the metal salt of jojoba oil fatty acid is at least one metal salt selected from the group consisting of sodium, potassium, calcium, magnesium, barium, zinc, lead, manganese, iron, nickel, cobalt, and aluminum.
It is preferable that the meadowfoam oil derivative is at least one selected from the group consisting of meadowfoam oil fatty acid, a metal salt of meadowfoam oil fatty acid, meadowfoam oil fatty acid ester, hydrogenated meadowfoam oil, meadowfoam oil amide, homomeadowfoam oil amide, meadowfoam oil triester, maleic acid derivatives of epoxidized meadowfoam oil, and isocyanate polymer of meadowfoam oil fatty acid polyhydric alcohol ester.
It is preferable that the meadowfoam oil triester is obtained by epoxidizing meadowfoam oil, hydrating the resultant product for ring-opening, and effecting acylation.
It is preferable that the metal salt of meadowfoam oil fatty acid is at least one metal salt selected from the group consisting of sodium, potassium, calcium, magnesium, barium, zinc, lead, manganese, iron, nickel, cobalt, and aluminum.
It is preferable that the toner further comprises an inorganic external additive.
It is preferable that the inorganic external additive is silica fine powder.
It is preferable that the silica fine powder is treated or coated with silicone oil.
It is preferable that the silica fine powder has a BET specific surface area by nitrogen adsorption of 30 to 350 m2/g.
It is preferable that the silica fine powder has a weight average particle diameter of 5 to 100 nm.
It is preferable that the toner comprises 0.1 to 10 parts by weight of the inorganic external additive per 100 parts by weight of the binding resin.
It is preferable that the binding resin has a weight average molecular weigh Mw of the toner of 100000 to 600000, a ratio Mw/Mn of the weight average molecular weight Mw to a number average molecular weight Mn of 50 to 100, a ratio Mz/Mn of a Z average molecular weight Mz to the number average molecular weight Mn of 350 to 1200, and a 1/2 outflow temperature measured by a koka-type flow tester of 100 to 145xc2x0 C.
It is preferable that the binding resin is polyester resin obtained by condensation polymerization between polycarboxylic acid or a lower alkyl ester thereof and polyhydric alcohol, having a weight average molecular weight Mw is 10000 to 300000, a ratio Mw/Mn of the weight average molecular weight Mw to a number average molecular weight Mn is 3 to 50, a ratio Mz/Mn of the Z average molecular weight Mz to the number average molecular weight Mn is 10 to 800, a 1/2 outflow temperature measured by a koka-type flow tester is 80 to 150xc2x0 C., and an outflow start temperature is 80 to 120xc2x0 C.
It is preferable that the binding resin comprises a copolymer obtained by copolymerizing at least a styrene based monomer and a monomer represented by Formula 1:
Formula 1 
(where R1 is a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and R2 is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a hydroxylalkyl group having 1 to 12 carbon atoms, or a vinylester group).
It is preferable that the binding resin comprises a copolymer obtained by copolymerizing at least a styrene based monomer and monomers represented by Formulae 2 and 3:
Formula 2 
(where R1 is a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and R2 is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a hydroxylalkyl group having 1 to 12 carbon atoms, or a vinylester group);
Formula 3 
(where R1 is a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and R3 is an alkyl group having 16 to 25 carbon atoms).
It is preferable that the binding resin comprises a copolymer obtained by copolymerizing at least a styrene based monomer and monomers represented by Formulae 4 and 5:
Formula 4 
(where R1 is a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and R2 is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a hydroxylalkyl group having 1 to 12 carbon atoms, or a vinylester group);
Formula 5 
(where R1 is a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and R4 is CnH2n (n: 1 to 5), and R5 is a lower alkyl group having 1 to 5 carbon atoms).
It is preferable that the toner further comprises a magnetic body in a toner base.
It is preferable that the magnetic body has an average particle size of 0.02 to 2.0 xcexcm, a ratio D25/D75 of 25% residual diameter D25 to 75% residual diameter D75 of 1.3 to 1.7, a BET specific surface area by nitrogen adsorption of 0.5 to 80 m2/g, an electrical resistance of 102 to 1011 xcexa9cm, a bulk density of 0.3 to 0.9 g/cc and a compression ratio of 30 to 80%, a capacity of absorbing linseed oil in an amount of 10 to 30 ml/100 g, a remnant magnetization of 5 to 20 emu/g, and a saturation magnetization of 40 to 80 emu/g.
It is preferable that the magnetic body is treated with at least one coupling agent selected from the group consisting of a titanium based coupling agent, a silane based coupling agent, an epoxysilane coupling agent, an acrylsilane coupling agent, and an aminosilane coupling agent.
It is preferable that in the toner constituting a two component developer together with a carrier, the carrier has a volume resistance of 108 to 1014 xcexa9cm, and has a coating layer of at least one resin selected from the group consisting of an acrylic based resin and a silicone based resin on a surface of magnetic core particles, and the magnetic core particles are at least one selected from the group consisting of Mn ferrite, Mnxe2x80x94Mg ferrite, and Lixe2x80x94Mn ferrite.
It is preferable that the inorganic external additive comprises silica and at least one substance selected from the group consisting of metal oxide fine powder and metal acid salt fine powder.
It is preferable that the metal acid salt fine powder comprises at least one selected from the group consisting of titanate based fine powder and zirconate based fine powder, each having an average particle size of 0.02 to 4 xcexcm and a BET specific surface area by nitrogen adsorption of 0.1 to 100 m2/g.
It is preferable that the metal acid salt fine powder is prepared by one method selected from the group consisting of a hydrothermal method or an oxalate thermal decomposition method.
It is preferable that the metal oxide fine powder comprises at least one selected from the group consisting of titanium oxide fine powder, aluminum oxide fine powder, strontium oxide fine powder, tin oxide fine powder, zirconium oxide fine powder, magnesium oxide fine powder, and indium oxide fine powder, each having an average particle size of 0.02 to 2 xcexcm, a BET specific surface area by nitrogen adsorption of 0.1 to 100 m2/g and an electrical resistivity of not more than 109 xcexa9cm.
It is preferable that the metal oxide fine powder is at least one fine powder selected from the group consisting of titanium oxide fine powder and silica oxide fine powder whose surface is coated with a mixture of tin oxide and antimony, each having a BET specific surface area by nitrogen adsorption of 1 to 200 m2/g.
It is preferable that the metal oxide fine powder comprises a magnetic body having an average particle size of 0.02 to 2.0 xcexcm, a ratio D25/D75 of 25% residual diameter D25 to 75% residual diameter D75 of 1.3 to 1.7, a BET specific surface area by nitrogen adsorption of 0.5 to 80 m2/g, an electrical resistance of 102 to 1011 xcexa9cm, a bulk density of 0.3 to 0.9 g/cc and a compression ratio of 30 to 80%, a capacity of absorbing linseed oil in an amount of 10 to 30 ml/100 g, a remnant magnetization of 5 to 20 emu/g, and a saturation magnetization of 40 to 80 emu/g.
A second toner of the present invention comprises silica fine powder, wherein the content of a component having a polydimethyl siloxane skeleton in the silica fine powder that is extracted by an organic solvent is not more than 2.5 wt %.
It is preferable that the silica has a BET specific surface area by nitrogen adsorption of 30 to 350 m2/g, and is treated or coated with one silicone oil selected from the group consisting of dimethyl silicone oil, methyl phenyl silicone oil, alkyl modified silicone oil, fluorine modified silicone oil, amino modified silicone oil, and epoxy modified silicone oil.
It is preferable that the toner comprises a toner base including a binding resin and a colorant.
It is preferable that the content of a component having a polydimethyl siloxane skeleton in the toner that is extracted by an organic solvent is not more than 0.09 wt %.
It is preferable that the binding resin has a weight average molecular weigh Mw in a molecular weight distribution of 100000 to 600000, a ratio Mw/Mn of the weight average molecular weight Mw to a number average molecular weight Mn of 50 to 100, a ratio Mz/Mn of a Z average molecular weight Mz to the number average molecular weight Mn of 350 to 1200, and a 1/2 outflow temperature measured by a koka-type flow tester of 100 to 145xc2x0 C.
It is preferable that the binding resin comprises a copolymer obtained by copolymerizing at least a styrene based monomer and a monomer represented by Formula 6:
Formula 6 
(where R1 is a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and R2 is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a hydroxylalkyl group having 1 to 12 carbon atoms, or a vinylester group).
It is preferable that the binding resin comprises a copolymer obtained by copolymerizing at least a styrene based monomer and monomers represented by Formulae 7 and 8:
Formula 7 
(where R1 is a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and R2 is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a hydroxylalkyl group having 1 to 12 carbon atoms, or a vinylester group);
Formula 8 
(where R1 is a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and R3 is an alkyl group having 16 to 25 carbon atoms).
It is preferable that the binding resin comprises a copolymer obtained by copolymerizing at least a styrene based monomer and monomers represented by Formulae 9 and 10:
Formula 9 
(where R1 is a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and R2 is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a hydroxylalkyl group having 1 to 12 carbon atoms, or a vinylester group);
Formula 10 
(where R1 is a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and R4 is CnH2n (n: 1 to 5), and R5 is a lower alkyl group having 1 to 5 carbon atoms).
A first method for producing a toner of the present invention comprises the steps of pre-blending a toner base component material comprising at least a binding resin and a colorant, kneading the toner base, pulverizing the same, classifying the produced colored particles to cut off powder toner for a predetermined particle size distribution, wherein an ester based wax is added to the binding resin before the pre-blending step.
It is preferable that in the method, the ester based wax is at least one substance selected from the group consisting of meadowfoam oil derivatives and jojoba oil derivatives.
It is preferable that in the method, the binding resin comprises a main component obtained by adding at least one compound selected from the group consisting of meadowfoam oil derivatives and jojoba oil derivatives to a binding resin solution, and removing a solvent.
It is preferable that in the method, the binding resin is polyester resin obtained by condensation polymerization between polycarboxylic acid or a lower alkyl ester thereof and polyhydric alcohol, having a weight average molecular weight Mw of 10000 to 300000, a ratio Mw/Mn of the weight average molecular weight Mw to a number average molecular weight Mn of 3 to 50, a ratio Mz/Mn of the Z average molecular weight Mz to the number average molecular weight Mn of 10 to 800, a 1/2 outflow temperature measured by a koka-type flow tester of 80 to 150xc2x0 C., and an outflow start temperature of 80 to 120xc2x0 C.
It is preferable that in the method, the powder toner that is cut off by the classification step is returned to the pre-blending step again, and reused to be pre-blended with the toner base component material.
It is preferable that a ratio of the powder toner that is cut off by the classification to the toner base component material is 2:98 to 40:60.
It is preferable that in the method, the toner comprises an ester based wax having an iodine value of not more than 25 and a saponification value of 30 to 300.
It is preferable that in the method, the toner comprises a polyolefin wax that is graft modified with unsaturated carboxylic acid and has an oxygen number of 6 to 200 mgKOH/g.
A second method for producing a toner of the present invention comprises silica fine powder, wherein the content of a component having a polydimethyl siloxane skeleton in the silica fine powder that is extracted by an organic solvent is not more than 2.5 wt %, and a toner base is subjected to a melting treatment by hot air, and then an external additive is added and mixed with the toner base.
It is preferable that in the method, at least one substance selected from the group consisting of hydrophobic silica, metal oxide fine powder and metal acid salt fine powder is mixed and adhered to the toner base, and then a surface improvement treatment is performed by hot air.
It is preferable that in the method, at least one substance selected from the group consisting of hydrophobic silica, metal oxide fine powder and metal acid salt fine powder is mixed and adhered to the toner base, and then a surface improvement treatment is performed with hot air, and the method further comprises the step of performing a treatment of external addition of at least one substance selected from the group consisting of hydrophobic silica, metal oxide fine powder and metal acid salt fine powder.
As described above, according to the present invention, the toner includes meadowfoam oil derivatives and/or jojoba oil derivatives, and silica fine powder whose content of a component having a polydimethyl siloxane skeleton is not more than 2.5 wt % is added externally to the toner base. Therefore, this embodiment stabilizes the chargeability and the flowability of the toner when used for a long period and eliminates the filming on a photoconductive member or a transfer medium. Moreover, the toner has a good fixing property and anti-offset property and allows recycling of waste toner and efficient transfer, and such toner can be obtained with high reproducibility.
Furthermore, the toner of the present invention can be used suitably in the following electrophotographic method. A plurality of movable image formation units for forming toner images for different colors are provided to form a circle, forming a group of image formation units, and all the image formation units move while rotating as one unit. This structure can achieve high density and low background fog and prevent the filming on the photoconductive member. Furthermore, when the toner of the present invention is used in an electrophotographic apparatus including a transfer system employing an intermediate transfer member, thinning-out or scattering can be prevented so as to achieve high transfer efficiency. Furthermore, in fixing four color toners, the toner of the present invention has good fixability, anti-offset properties and glossiness without oil.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.